Device for providing clean combustion air for the internal combustion engine of a working tool

ABSTRACT

In a device for providing clean combustion air for an internal combustion engine of a working tool, provision is made for a cyclone filter into which ambient air contaminated with impurities can be sucked. A partial air flow contaminated with impurities can be extracted by suction from the cyclone filter, a partial air flow substantially freed from impurities is branched off from the cyclone filter and supplied to the internal combustion engine as combustion air. A fan which provides a flow of cooling air against the internal combustion engine, is at least partially accommodated in a housing. Provision is made in the housing for at least one suction bore, which leads into the housing and provision is made in the area of the suction bore for a flow element for creating a low pressure. The partial air flow contaminated with impurities is connected to the suction bore.

The instant invention relates to a device for providing clean combustionair for the internal combustion engine of a working tool, in particularof a handheld working tool, such as a chainsaw, an angle grinder, aworking tool for the yard and landscape maintenance and the like,wherein provision is made for a cyclone filter, into which ambient air,which is contaminated with impurities, can be sucked, wherein a partialair flow, which is contaminated with impurities, can be extracted bysuction from the cyclone filter, wherein a partial air flow, which issubstantially freed from impurities, is furthermore branched off fromthe cyclone filter and can be supplied to the internal combustion engineas combustion air, and wherein provision is made for a fan, by means ofwhich cooling air can flow against the internal combustion engine andwherein the fan is at least partially accommodated in a housing.

PRIOR ART

A device for providing clean combustion air for the internal combustionengine of a working tool, which is embodied as an angle grinder, forexample, is known from DE 10 2004 058 136 A1. The device comprises acyclone filter, into which ambient air, which is contaminated withimpurities, is sucked, wherein a partial air flow, which is contaminatedwith impurities, is extracted by suction from the cyclone filter,wherein the extraction by suction is created by means of a low pressure,which is created by means of the rotary motion of a fan. For thispurpose, the fan encompasses a so-called rear blading, through which, inan outlet port, into which the partial air flow that is contaminatedwith impurities leads, is sucked. Disadvantageously, an installationspace is required for the rear blading of the fan, and the front bladingof the fan, which serves to provide a cooling air, by means of which theinternal combustion engine, in particular the cylinder of the internalcombustion engine is cooled, must be embodied so as to be smaller due tothe limited installation space of the fan in a housing, whereby only asmaller quantity of cooling air can be provided to the internalcombustion engine.

A further device for providing clean combustion air for the internalcombustion engine of a working tool, which is also embodied as an anglegrinder, for example, is known from DE 20 2006 002 330 U1. To create apartial air flow, which is contaminated with impurities, for a cyclonefilter, a low pressure is also provided by means of a fan, whichsubstantially serves to cool the internal combustion engine and inparticular the cylinder of the internal combustion engine. A bore, whichis fluidically connected to the partial air flow of the cyclone filter,which is contaminated with impurities, is created in the central axis ofrotation of the fan. In the event that the fan is rotated, for examplein that the fan is connected to the crankshaft of the internalcombustion engine, a low pressure that finally serves to extract thepartial air flow, which is contaminated with impurities, from thecyclone filter by means of suction, is created in the hub of the fan.Disadvantageously, the suction effect is limited by means of such anarrangement via the hub of the fan.

DESCRIPTION OF THE INVENTION Object, Solution, Advantages

It is thus the object of the instant invention to further develop adevice for providing clean combustion air for the internal combustionengine of a motorized working tool such that said device is embodied soas to save installation space and so as to be efficient. It is inparticular the object of the instant invention not to use any additionalelements, by means of which the low pressure is created in the partialair flow, which is contaminated with impurities.

This object is solved based on a device for providing clean combustionair according to the preamble of claim 1, based on a method forproviding clean combustion air according to the preamble of claim 9 andbased on a working tool comprising a device for providing cleancombustion air according to claim 11, in each case with the respectivecharacterizing features. Advantageous further developments of theinvention are specified in the dependent claims.

The invention includes the technical teaching that provision is made inthe housing for at least one suction bore, which leads into the housingand that provision is made in the area of the suction bore for a flowelement for creating a low pressure, wherein the partial air flow, whichis contaminated with impurities, is connected to the suction bore.

The invention is based on the idea of forming a Venturi nozzle, by meansof which a low pressure can be created in the known manner, by means ofa suction bore and a flow element in the housing, in which the fan isaccommodated. For this purpose, provision is made according to theinvention in the housing for a suction bore, which leads into the area,in which the fan is accommodated in the housing. In the event that theinternal combustion engine of the working tool is operated, the fantypically rotates permanently about an axis, which is formed by means ofthe crankshaft of the internal combustion engine, for example. A lowpressure is thus permanently provided in the suction bore, which can beconnected to the cyclone filter. The connection between the suction boreof the Venturi nozzle in the housing and the cyclone filter can beestablished by means of a hose connection or by means of a pipeconnection, by means of which the partial air flow, which iscontaminated with impurities, is created. The contaminated partial airflow can thus be extracted by suction from the cyclone filter and can beguided into the housing, and the air flow in the housing, which iscreated by means of the fan, only serves to cool the internal combustionengine, in particular the cylinder of the internal combustion engine.This does not disadvantageously impact the function of the internalcombustion engine and the formed Venturi nozzle does not require anyadditional installation space. An effective separation of impuritiesfrom the partial air flow, which is supplied to the internal combustionengine as combustion air, for example after passing through a furtherfilter for fine-dedusting, can be ensured due to the high suction effectin the suction bore by utilizing the Venturi nozzle effect.

For example, the housing can encompass a flow chamber, in which the fanis arranged so as to rotate about an axis, wherein the suction boreleads into the flow chamber, in particular wherein the fan creates anair flow in the mouth area of the suction bore. The flow chamber canencompass a snail shell-like contour, for example, and the suction borecan be embodied so as to be oriented radially towards the axis of thefan, for example. In the alternative, the suction bore in the bottomwall of the housing can extend parallel to the axis of the fan. The fancan be embodied as tangential fan, so that the fan wheel is flownagainst approximately axially, for example, and the air to be suppliedto the internal combustion engine is initially accelerated into a rotarymotion about the axis, so that the air flow is created in the mouth areaof the suction bore. The air flow can subsequently leave the fan areaapproximately tangentially, wherein at least one suction bore canpreferably be introduced into an area in the housing, in which the airflow is particularly strong, so as to create a correspondingly strongsuction effect in the suction bore.

By providing the low pressure for the partial air flow, which iscontaminated with impurities, according to the invention by arranging aVenturi nozzle in the housing for accommodating the fan, theconstruction of a fan is made possible, which is only equipped on oneside with fan blades, which serve to create the air flow in the moutharea of the suction bore. By means of the one-sided blading of the fan,the air flow for cooling the internal combustion engine can be embodiedin a particularly strong manner, because the fan blades can be embodiedso as to be larger than when the fan encompasses a rear blading, whichwould only serve to create a low pressure.

According to a possible advantageous embodiment of the flow element, itcan form a constriction contour in a housing part of the housing, inparticular in the housing part, into which the suction bore leads,and/or the constriction contour is embodied so as to be located oppositethe mouth of the suction bore in the housing. In both arrangements, alow pressure can be created in the mouth area of the suction bore,because the air flow in the housing is accelerated by means of the flowconstriction, whereby the suction effect is created.

The flow element, which is embodied as constriction contour, canencompass the profile of an upper wing side of an airfoil wing, forexample, wherein the suction bore leads into the flow chamber,downstream from the highest profile point in the upper wing side. Aparticularly strong suction effect is utilized through this, because thestrongest low pressure prevails downstream from the highest profilepoint in the upper wing side. The constriction contour in the form of anupper wing side can already be embodied in the injection molding of aplastic housing, for example, so that the housing itself forms theconstriction contour. In the alternative, an additional component can bearranged on the inner side of the housing, into which the suction borehas already been introduced for forming the constriction contour.

According to a further possible embodiment, the flow element can beembodied as airfoil wing profile, which is arranged close to the mouthof the suction bore in the housing, here in particular in the flowchamber. The airfoil wing profile can thereby be arranged in the flowchamber, so that the air flow can flow completely around it at leastfrom a bottom wing side and from an upper wing side. The flow element inthe form of an airfoil wing profile thus does not only need to beembodied as contour in the housing, but the airfoil wing profile canalso be arranged freely in the flow chamber, and a low pressure iscreated in particular on the upper wing side, so that the airfoil wingprofile can be arranged in the air flow, with the upper wing side facingin the direction of the suction bore. It goes without saying that afirst flow element, which is embodied as constriction contour in thehousing, and a second flow element, which is embodied so as to bearranged freely in the flow chamber as airfoil wing profile, can becombined with one another.

The instant invention is further directed to a method for providingclean combustion air for an internal combustion engine of a workingtool, in particular of a handheld working tool, such as a chainsaw, anangle grinder, a working tool for the yard and landscape maintenance andthe like, wherein provision is made for a cyclone filter, into whichambient air, which is contaminated with impurities, is sucked, wherein apartial air flow, which is contaminated with impurities, is extracted bysuction from the cyclone filter, and wherein a partial air flow, whichis substantially freed from impurities, is furthermore branched off fromthe cyclone filter and is supplied to the internal combustion engine ascombustion air, and wherein provision is made for a fan, by means ofwhich cooling air flows against the internal combustion engine. The fanis at least partially accommodated in a housing, wherein at least onesuction bore is introduced into the housing and wherein a low pressureis created in the area of the suction bore in connection with at leastone flow element, wherein the partial air flow, which is contaminatedwith impurities, is extracted through the suction bore by suction bymeans of the low pressure. The features and advantages of theabove-described device can also be considered for the method accordingto the invention.

The invention is further directed to a working tool comprising a deviceaccording to the above-described type, in particular for operating amethod for providing clean combustion air for an internal combustionengine of the working device according to the above description.

BRIEF DESCRIPTION OF THE DRAWINGS

Further measures, which improve the invention, will be illustrated inmore detail below by means of the figures together with the descriptionof preferred exemplary embodiments of the invention.

FIG. 1 shows a perspective view of a working tool comprising a devicefor providing clean combustion air,

FIG. 2 shows a top view onto a first exemplary embodiment of a devicefor providing clean combustion air,

FIG. 3 shows a side view of the exemplary embodiment of the deviceaccording to FIG. 2 and

FIG. 4 shows a further exemplary embodiment of a device in a top view.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows an exemplary embodiment of a working tool 100 comprising aninternal combustion 11, which is not shown explicitly and which servesto drive a tool 25. The internal combustion engine 11 is supplied withan ambient air 13, which can pass through ventilating slits 26, whichare introduced into a housing 17 of the working tool 100. The housing 17serves primarily to accommodate a fan 16 and for correspondingly guidingan air flow 23 to the internal combustion engine 11, as is illustratedin more detail in the following figures.

In a top view, FIG. 2 shows a part of the working tool 100 according toFIG. 1 comprising a device 1 for providing clean combustion air to theinternal combustion engine 11. The housing 17 is illustrated without thehousing cover, which is shown with ventilating slits 26 in FIG. 1, andthe view shows a further housing part 17 a. A fan 16, which encompassesa plurality of fan blades 24, which are arranged on the front side ofthe fan wheel, is accommodated in this housing part 17 a so as to rotateabout an axis 22. The axis 22 can be formed by an end of the crankshaftof the internal combustion engine 11, for example. The housing part 17 aencompasses an accommodating depression for accommodating the fan 16,and the accommodating depression increases in a radially expandingmanner in the direction of the cylinder of the internal combustionengine 11, so that an approximately logarithmic spiral is created, and aflow chamber 21 is formed by means of it. A flow, which substantiallyrotates about the axis 22 and which is created by means of the guideblades 24 of the rotating fan 16, is created in this flow chamber 21.

According to the invention, a flow element 19 in the form of aconstriction contour 19 is embodied in the bottom area of the flowchamber 21, and two suction bores 18 lead into the constriction contour19. The air flow 23 accelerates above the constriction contour 19, sothat a low pressure is created in the air flow 23 according to Bernoulliand a suction is consequently created in the suction bores 18. Adetailed illustration of the device 1 for providing clean combustion air10 for the internal combustion engine 11 in particular in operativeconnection with the cyclone filter 12 is shown in FIG. 3 in more detail.

FIG. 3 shows a side view of the housing 17, in which the non-illustratedfan 16 is accommodated. The cross sectional view of the housing part 17a of the housing 17 illustrates the constriction contour 19, throughwhich the suction bore 18 extends and which leads into the flow chamber21, viewed in flow direction, downstream from the highest profile point27. The illustration of the air flow 23 shows an acceleration area ofthe flow above the constriction contour 19, so that a low pressure iscreated in the mouth area of the suction bore 18.

A cyclone filter 12, into which ambient air 13 is sucked, which iscontaminated with impurities, is furthermore shown. A partial air flow14 is fluidically connected to the suction bore 18, and air, which iscontaminated with impurities, can be extracted by suction from thecyclone filter 12 via the partial air flow 14 by means of the lowpressure, which is created in the mouth area of the suction bore 18. Theembodiment of a Venturi nozzle is thereby created by means of thearrangement of the suction bore 18 in combination with the constrictioncontour 19, and contaminated air is extracted by suction from thecyclone filter 12 via the partial air flow 14 by means of the Venturieffect.

A further partial air flow 15 leaves the cyclone filter 12 in a state,which is substantially freed from impurities, and the partial air flow15, which is pre-cleaned by means of the cyclone filter 12, isfine-dedusted by means of a further filter 28, which is embodied aspaper filter or fabric filter, for example, and the combustion air 10,which is provided with this, can be supplied to the internal combustionengine 11.

FIG. 4 shows a further exemplary embodiment of a device 1 for providingclean combustion air 10 for the internal combustion engine 11 of a worktool 100 according to FIG. 1. The illustration shows the housing part 17a of the housing 17, as it is part of the working tool 100 according toFIG. 1. The fan 16 is accommodated in the housing part 17 a so as torotate about the axis 22, and the fan 16 encompasses fan blades 24 forcreating an air flow 23 in the flow chamber 21, which is formed in thehousing part 17 a. A suction bore 18, which leads into the flow chamber21 and thus into the air flow 23, is introduced into the wall of thehousing part 17A. As shown in an implied manner, the suction bore 18 isin turn connected to the partial air flow 14 of the cyclone filter 12,through which ambient air 13 is sucked in. The partial air flow 14 isthereby contaminated with impurities and the further provided partialair flow 15 is pre-cleaned and can be supplied to the internalcombustion engine 11 of the working tool 100 as combustion air 10 afterpassing through the filter 28.

The flow element 20 is embodied as airfoil wing profile 20 and isinserted in the flow chamber 21 at a distance upstream of the mouth areaof the suction bore 18. In the event that the air flow 23 flowscompletely around the airfoil wing profile 20, an acceleration of theair flow 23 is created on the upper side of the airfoil wing profile 20,which faces in the direction of the suction bore 18, whereby a lowpressure is in turn created again in the mouth area of the suction bore18. Through this, contaminated air can be extracted by suction from thecyclone filter 12 via the partial air flow 14 in the manner, which hasalready been described, wherein the impurities enter into the air flow23, which substantially serves only to cool the internal combustionengine 11.

The embodiment of the invention is not limited to the exemplaryembodiments, which have only been shown in an exemplary manner above.Instead, a number of alternatives is possible, which utilizes theillustrated solution even in the case of embodiments, which are of agenerally different type. All of the features and/or advantages, whichfollow from the claims, the description or the drawings, includingstructural details or spatial arrangements, can be significant for theinvention, both alone and in a variety of combinations. In particular,the flow element, embodied in an exemplary manner as constrictioncontour 19 or as airfoil wing profile 20, can be embodied in any otherway so as to create a low pressure in the mouth area of the suction bore18. In particular, provision can also be made in a flow path of the airflow 23 from the fan 16 to the internal combustion engine 11 for asection, which is geometrically embodied in another way such that theVenturi effect can be utilized, so as to create a low pressure on theside of the partial air flow 14 of the cyclone filter 12. The inventionis thus not limited to the arrangement of a corresponding flow geometryin the housing part 17A, and it is possible, for example, to alsoprovide a geometric embodiment for utilizing a Venturi effect in abypass. For example, the cyclone filter 21 can geometrically adjoin theflow chamber 21 with only one intermediate wall such that a connectionas hose line or pipeline for the partial air flow 14 is no longernecessary, and a connection between the cyclone filter 12 and the flowchamber 21 can be limited to the suction bore 18. A combination of theflow elements 19 and 20 is furthermore possible, so that an airfoil wingprofile 20 can be provided so as to be spaced apart from a constrictioncontour 19, wherein both flow elements 19 and 20 are arranged in the airflow 23.

LIST OF REFERENCE NUMERALS

-   100 working tool-   1 device-   10 combustion air-   11 internal combustion engine-   12 cyclone filter-   13 ambient air-   14 partial flow contaminated-   15 partial flow clean-   16 fan-   17 housing-   17 a housing part-   18 suction bore-   19 flow element, constriction contour-   20 flow element, airfoil wing profile-   21 flow chamber-   22 axis-   23 air flow-   24 fan blade-   25 tool-   26 ventilating slits-   27 highest profile point-   28 filter

1. A device for providing clean combustion air for the internalcombustion engine of a working tool, in particular of a handheld workingtool, such as a chainsaw, an angle grinder, a working tool for the yardand landscape maintenance and the like, wherein provision is made for acyclone filter, into which ambient air, which is contaminated withimpurities, can be sucked, wherein a partial air flow, which iscontaminated with impurities, can be extracted by suction from thecyclone filter, wherein a partial air flow, which is substantially freedfrom impurities, is furthermore branched off from the cyclone filter andcan be supplied to the internal combustion engine as combustion air, andwherein provision is made for a fan, by means of which cooling air canflow against the internal combustion engine and wherein the fan is atleast partially accommodated in a housing, characterized in thatprovision is made in the housing for at least one suction bore, whichleads into the housing and that provision is made in the area of thesuction bore for a flow element for creating a low pressure, wherein thepartial air flow, which is contaminated with impurities, is connected tothe suction bore.
 2. The device according to claim 1, characterized inthat the housing encompasses a flow chamber, in which the fan isarranged so as to rotate about an axis, wherein the suction bore leadsinto the flow chamber, in particular wherein the fan creates an air flowin the mouth area of the suction bore.
 3. The device according to claim1, characterized in that the air flow serves to flow against theinternal combustion engine and in particular the cylinder of theinternal combustion engine.
 4. The device according to claim 1,characterized in that the fan is equipped on one side with fan blades,which serve to create the air flow in the mouth area of the suctionbore.
 5. The device according to claim 1, characterized in that the flowelement is embodied as constriction contour in a housing part of thehousing, in particular into which the suction bore leads and/or theconstriction contour is embodied so as to be located opposite the mouthof the suction bore in the housing.
 6. The device according to claim 5,characterized in that the flow element, which is embodied asconstriction contour, encompasses a profile of an upper wing side of anairfoil wing, wherein the suction bore leads into the flow chamber,preferably downstream from the highest profile point in the upper wingside.
 7. The device according to claim 1, characterized in that the flowelement is embodied as airfoil wing profile, which is arranged close tothe mouth of the suction bore in the housing, in particular in the flowchamber.
 8. The device according to claim 7, characterized in that theairfoil wing profile is arranged so that the air flow can flowcompletely around it at least from a bottom wing side and from an upperwing side, in particular wherein the airfoil wing profile is arranged inthe air flow, with the upper wing side facing in the direction of thesuction bore.
 9. A method for providing clean combustion air for aninternal combustion engine of a working tool, in particular of ahandheld working tool, such as a chainsaw, an angle grinder, a workingtool for the yard and landscape maintenance and the like, whereinprovision is made for a cyclone filter, into which ambient air, which iscontaminated with impurities, is sucked, wherein a partial air flow,which is contaminated with impurities, is extracted by suction from thecyclone filter, wherein a partial air flow, which is substantially freedfrom impurities, is furthermore branched off from the cyclone filter andis supplied to the internal combustion engine as combustion air, andwherein provision is made for a fan, by means of which cooling air flowsagainst the internal combustion engine and wherein the fan is at leastpartially accommodated in a housing, characterized in that at least onesuction bore is introduced into the housing and wherein a low pressureis created in the area of the suction bore in connection with at leastone flow element, wherein the partial air flow, which is contaminatedwith impurities, is extracted by suction by means of the low pressurethrough the suction bore.
 10. The method according to claim 9 forproviding clean combustion air for an internal combustion engine of aworking tool comprising a device for providing clean combustion air forthe internal combustion engine of a working tool, in particular of ahandheld working tool, such as a chainsaw, an angle grinder, a workingtool for the yard and landscape maintenance and the like, whereinprovision is made for a cyclone filter, into which ambient air, which iscontaminated with impurities, can be sucked, wherein a partial air flow,which is contaminated with impurities, can be extracted by suction fromthe cyclone filter, wherein a partial air flow, which is substantiallyfreed from impurities, is furthermore branched off from the cyclonefilter and can be supplied to the internal combustion engine ascombustion air, and wherein provision is made for a fan, by means ofwhich cooling air can flow against the internal combustion engine andwherein the fan is at least partially accommodated in a housing,characterized in that provision is made in the housing for at least onesuction bore, which leads into the housing and that provision is made inthe area of the suction bore for a flow element for creating a lowpressure, wherein the partial air flow, which is contaminated withimpurities, is connected to the suction bore.
 11. A working toolcomprising a device according to claim 1, in particular for operating amethod for providing clean combustion air for an internal combustionengine of the working tool, in particular of a handheld working tool,such as a chainsaw, an angle grinder, a working tool for the yard andlandscape maintenance and the like, wherein provision is made for acyclone filter, into which ambient air, which is contaminated withimpurities, is sucked, wherein a partial air flow, which is contaminatedwith impurities, is extracted by suction from the cyclone filter,wherein a partial air flow, which is substantially freed fromimpurities, is furthermore branched off from the cyclone filter and issupplied to the internal combustion engine as combustion air, andwherein provision is made for a fan, by means of which cooling air flowsagainst the internal combustion engine and wherein the fan is at leastpartially accommodated in a housing, characterized in that at least onesuction bore is introduced into the housing and wherein a low pressureis created in the area of the suction bore in connection with at leastone flow element, wherein the partial air flow, which is contaminatedwith impurities, is extracted by suction by means of the low pressurethrough the suction bore.